Populations, Communities, and Species Interaction Chapter 3.
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Transcript of Populations, Communities, and Species Interaction Chapter 3.
Outline:
• Critical Factors and Tolerance Limits• Adaptation and Natural Selection• Speciation• Ecological Niche• Species Interaction• Population Growth• Community Properties and Structure• Succession
Critical Factors and Tolerance Limits
• Critical Factor - Single factor in shortest supply relative to demand is a critical determinant in species distribution. Tolerance Limits refer to minimum and
maximum levels beyond which a particular species cannot survive or reproduce.
- Many species exhibit tolerance limits that are more critical for young than adults.
Adaptation
• Adaptation - Process where species acquire traits that allow them to survive in their environments. Limited range of physiological modifications
(acclimation) – change not permanent. Inheritance of specific genetic traits allowing
a species to live in a particular environment.- Population-level phenomenon – traits
passed on. Evolution – species change gradually
thru competition for scarce resources
Natural Selection
• Natural Selection - Describes process where better competitors survive and reproduce more successfully. Small, spontaneous, random mutations
occur in every population creating genetic diversity.
Limited resources or environmental conditions may exert selective pressure on a population.
Mutations – may be negative or positive
Factors Exerting Selective Pressure
• Physiological stress due to in-appropriate levels of a critical environmental factor. Moisture, Light, pH
• Predation Including parasitism & disease
• Competition• LUCK
Speciation
• Given enough time, mutations may collectively allow a species to become better suited to new environmental conditions. Divergent evolution - Separation of one
species into new species. Convergent evolution - Unrelated
organisms evolve to look and act alike.
Ecological Niche
• Habitat - Set of environmental conditions in which a particular organism lives.
• Ecological Niche – description of either- The role played by a species in a
biological community, or- Total set of environmental factors that
determines species distribution. Generalists - Broad niche Specialists - Narrow niche
Resource PartitioningLaw of competitive exclusion – no two populations of different species will occupy the same niche and compete for exactly the same resources in the same habitat for very long
So they migrate, or adapt to partition the resources, or die!
Ecological Niche
• Resource Partitioning - Alter behavior or physiology to minimize competition. Allows several species to utilize different
parts of the same resource.